The invention concerns balustrades for staircases and the like, the balustrades being of the type including balusters provided at their upper ends with fastening elements so designed that they can mount a handrail interval and impart thereto an adjustable angle of handrail incline. Such balustrades furthermore include a handrail made up of a succession of handrail intervals that extend at angles to one another and have different respective inclinations. Each end of a handrail interval has a vertical end face. Means are provided in the region of each such vertical end face for joining the handrail interval to the next-following handrail interval.
Staircases generally require balustrades for the safety of persons using them. Staircases that have floor or inter-floor landings and change in direction and/or in angle of rise after such a landing require correspondingly configured handrails. There are many approaches to the problem of providing an easily assembled handrail construction that can be adapted to the differing angular directions and angles of inclination that successive handrail intervals are to exhibit in an arbitrary case. In general, however, each such known approach tends to be oriented, or is simply limited, to the use of one or more particular structural materials, whether metal, plastic, rope, or whatever. Handrails made of such materials present to the user's hand a subjective feel or grip very perceptibly differing from that of wood handrails. For a variety of reasons, many users of staircases and many builders strongly prefer handrails made of wood. Even the sight of a wooden handrail communicates a certain sense of familiarity and reliability, and the use of one during staircase ascent or descent gives the already mentioned and very characteristic wood-handrail feel that is so desirable. In very many instances today, the use of wood for handrails is economically feasible exclusively where straight handrail intervals are in question. Accordingly, staircases whose successive flights each extend in a different direction, such as long-L, narrow-U, and winder staircases, and likewise spiral and circular staircases, etc., are very often provided with handrails entirely constituted by a series of connected together, straight-extending handrail intervals. In those instances where one knows in advance, and with a high degree of precision and accuracy, the angular directions and angles of incline of the various straight intervals of a complex handrail, then in certain cases the handrail, or at least substantial parts of it, can be prefabricated at a factory, utilizing calculating, manufacturing, and assembling equipment, often under numerical or computer control. However, experience has proved that, in situations where the staircase must be fitted on site, in order to take into account dimensional tolerances of neighboring structural members, the handrail for the staircase must likewise be assembled, and to a considerable degree fabricated, on site.
In situations where a flight of steps that extends in a single direction has, e.g., an intermediate horizontal interval due to the presence of an intermediate or inter-story landing, a corresponding and abrupt change of the inclination of the associated handrail, e.g., from a non-zero value to zero or vice versa, is readily achieved by one clean cut taken coincident with the bisector of the angle that is to be included between each two successive handrail intervals. However, experience shows that, when made on site, the cuts needed to implement the necessary changes of handrail direction and/or inclination inevitably exhibit various imperfections that can be quite problematic. These imperfections of cut may include, inter alia, chips and fractures at the edges of the cut end face of a handrail interval; burring along those edges; the presence of sometimes lengthy and deep-going surface splinters which extend to and are detached at the cut end face of the handrail interval and, at the ends of the splinters remote from the end face are still attached to the handrail stock but very tenuously; and so forth. These imperfections of cut are especially problematic if the successive handrail intervals are to be joined, one to the next, at their vertical end faces in face-to-face manner, and most especially when such joints are to exhibit sharp corners. Even the particular techniques developed for application to load-bearing stringers and stair carriages, but also applicable to handrails, that are disclosed in, e.g., Federal Republic of Germany "Gebrauchsmuster" DE-GM 71 73 304 and DE-GM 75 39 028 (the latter corresponding to published patent application, "Offenlegungsschrift", DE-OS 25 55 041) require very costly and exact manual work to form butt joints and seams that can be made to fit one another, with their formation requiring very clean cutting work.
In traditional staircase construction, it was of course customary to provide vertical handrail-supporting posts at the upper and lower ends of the stairway and at each landing, to support a handrail which would be of smoothly continuing character, no matter what the number of changes of handrail direction and inclination, and with the cross sections of the constituent handrail intervals being of whatever shape needed to achieve this. Clearly, the highly developed manual skills needed to accomplish such results are, nowadays, no longer available at reasonable cost.
Various attempts have been made to develop quick-assembly techniques in which handrails made of wood or wood-based materials are to be fitted onto successive staircase flights, where the successive flights necessitate handrail intervals of differing inclination, and in which the constituent handrail intervals are so far as possible prefabricated. Irrespective of whether such attempts at quick-assembly aspired to traditional, smoothly continuous handrail appearance, or to an appearance differing greatly therefrom, the fitting together of individual component elements on-site has been impossible to avoid, and with even the best of these attempts a certain degree of difficulty, requiring a certain degree of skill on the part of the joiners, has likewise been impossible to avoid. It will often happen that, earlier or later in the on-site assembly process, it is discovered that elements to be fitted together do not fit together because of already made assembly decisions or errors. Accordingly it is important that, when performing such on-site assembly of prefabricated elements, one be able to re-do sometimes substantial portions of already done assembly work without leaving behind visible traces of the original, unsuccessful attempts at assembly.